Author Topic: Early 90s Bowling Scorer Board  (Read 5748 times)

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Offline james_s

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Re: Early 90s Bowling Scorer Board
« Reply #25 on: January 25, 2017, 01:28:22 am »
OK well first things first. Do you know how to interpret a video signal on the scope?

Triggering might be a bit tricky, but you should see something like this on the scope:


I'm going from memory as it's a loooong time since I worked on video, but the above represents a horizontal  line and should be at 15kHz-ish. The levels at the front/back porch should be ~0v which represents black or rather no colour for that channel. The negative going pulses are the sync and the waveform in between is the actual video. 0v=dark 700mV=max. (forget the color burst, that's for composite not RGB)

The 4066s will be for switching the video between sources so check them, and the digital switching signals on pins 5,6,12,13. One of the 4066 switches may also switch the video signal to 0v during the front or back porch, this is to ensure that "dark" is actually 0v and is what I was referring to earlier by DC clamping.

At least you have working boards to compare against which should make life a bit simpler!


What you show is a composite video signal, that won't be the case here because this is RGB. I've only worked on the monitors used in these systems because they're also used in arcade game cabinets but they use analog RGB that is typically 4V full on, 1V black, 0.8V blank and then TTL level sync which can be separate H-V or composite sync.

Look at the pins on each side of one of the switch elements in a 4066 and compare to the same points on a working board. Do this test in-system.
 

Offline RyanG

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Re: Early 90s Bowling Scorer Board
« Reply #26 on: January 26, 2017, 07:02:09 pm »
I've tried reading off the 4066s with no real luck. I only had that scope temporarily, so that's gone. Kind of stuck going nowhere now. I have enough spares to last a while hopefully
 

Offline james_s

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Re: Early 90s Bowling Scorer Board
« Reply #27 on: January 26, 2017, 07:31:32 pm »
What did you see? Are the control inputs toggling? A logic probe would be helpful here, they're cheap.
 

Offline RyanG

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Re: Early 90s Bowling Scorer Board
« Reply #28 on: January 26, 2017, 10:18:38 pm »
I didn't see much of anything happening on the scope besides the difference on the video output pins
 

Offline james_s

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Re: Early 90s Bowling Scorer Board
« Reply #29 on: January 27, 2017, 12:09:56 am »
Is the CPU running? Take a look at the Reset pin with a logic probe, a DMM will work in a pinch. If that's not in reset state have a peek at the address bus and see if it's doing anything.
 

Offline RyanG

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Re: Early 90s Bowling Scorer Board
« Reply #30 on: January 27, 2017, 01:26:56 am »
I'm pretty sure when I checked the reset pin before it was at 5v on both the good and bad boards.
 

Offline james_s

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Re: Early 90s Bowling Scorer Board
« Reply #31 on: January 27, 2017, 01:48:51 am »
Next thing to check is the address and data bus lines for activity. Keep in mind this may have to be done with the board operating in the equipment.
 

Offline RyanG

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Re: Early 90s Bowling Scorer Board
« Reply #32 on: February 09, 2017, 03:55:32 am »
Haven't replied in a little while, but I have had no luck with these boards. I am also working on a bunch of other electronics related projects as well as my normal mechanical stuff. Thanks for the help you guys have given.
 

Offline Cupcakus

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Re: Early 90s Bowling Scorer Board
« Reply #33 on: February 10, 2017, 07:03:08 am »
It's too bad no one on the board
 

Offline Cupcakus

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Re: Early 90s Bowling Scorer Board
« Reply #34 on: February 10, 2017, 07:04:48 am »
It's too bad no one on the boards is close enough to you to render aid, with just a bit more test equipment and know how I'm sure this could be tracked down.
 

Offline james_s

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Re: Early 90s Bowling Scorer Board
« Reply #35 on: February 10, 2017, 07:17:31 am »
Well I offered to take a look at one for the cost of postage.
 


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